Prepare for v2.3.1 release (#675)

Update README and addon.xml for release.

README.md

@@ -50,6 +50,13 @@ leave a message at [our Facebook page](https://facebook.com/kodivrtnu/).
 ![](./resources/media/screenshot04.jpg)
 
 ## Releases
+### v2.3.1 (2020-01-13)
+- Fix an issue related to type-handling for settings (@dagwieers)
+- Fix an issue related to marking played videos as watched when using Up Next (@mediaminister)
+- Small fix for livestreams (@mediaminister)
+- Improvements to metadata handling specific to Kodi rendering (@dagwieers)
+- Support multiple YouTube links per channel (@dagwieers)
+
 ### v2.3.0 (2020-01-01)
 - Add integration for Up Next add-on (@mediaminister)
 - Store resume points and watchlater at VRT NU (@dagwieers, @mediaminister)

addon.xml

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
-<addon id="plugin.video.vrt.nu" name="VRT NU" version="2.3.0" provider-name="Martijn Moreel, dagwieers">
+<addon id="plugin.video.vrt.nu" name="VRT NU" version="2.3.1" provider-name="Martijn Moreel, dagwieers">
 <requires>
   <import addon="resource.images.studios.white" version="0.0.22"/>
   <import addon="script.module.beautifulsoup4" version="4.6.2"/>
   <import addon="script.module.dateutil" version="2.8.0"/>
-  <import addon="script.module.inputstreamhelper" version="0.4.2"/>
+  <import addon="script.module.inputstreamhelper" version="0.4.3"/>
   <import addon="script.module.routing" version="0.2.3"/>
   <import addon="xbmc.python" version="2.25.0"/>
 </requires>
@@ -42,6 +42,13 @@
   <website>https://github.com/pietje666/plugin.video.vrt.nu/wiki</website>
   <source>https://github.com/pietje666/plugin.video.vrt.nu</source>
   <news>
+v2.3.1 (2020-01-14)
+- Fix an issue related to type-handling for settings
+- Fix an issue related to marking played videos as watched when using Up Next
+- Small fix for livestreams
+- Improvements to metadata handling specific to Kodi rendering
+- Support multiple YouTube links per channel
+
 v2.3.0 (2020-01-01)
 - Cosmetic changes to metadata and plot
 - Store resume points and watchlater at VRT NU
@@ -78,17 +85,6 @@ v2.2.0 (2019-08-14)
 - Fix play-by-airdate API interface
 - Add TV guide to channel menu
 - Add a context menu to remove search queries from history
-
-v2.1.1 (2019-07-20)
-- Fix issue on Kodi v17
-
-v2.1.0 (2019-07-11)
-- Fix an issue with roaming VRT tokens
-- Start a video by channel/start time
-- Use notifications for various events related to tokens/cache/credentials
-- Add YouTube channel support
-- Add Radio 1 live stream
-- Improve credential input
   </news>
   <assets>
     <icon>resources/media/icon.png</icon>